The need for effective herbicides, both preemergence and postemergence, needs no special emphasis. The control of weeds and undesirable vegetation is of great economic importance since weed competition inhibits the production of foliage, fruits and/or seeds and may reduce the quality of the harvested crop. Weed control is essential for maximum production of many agronomic and horticultural crops including corn (Zea mays L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oats (Avena sativa L.) and rice (Oryza sativa L.). Furthermore, weeds on noncropped areas may cause a fire hazard, undesirable drifting of sand or snow, or irritation to persons with allergies. Thus, suppression of undesirable weed growth is very advantageous.
Moreover, the need for agricultural chemicals having significant effects on the growth and development of crop plant species is similarly well known. One form of such plant growth regulation which is particularly economically important is the field of harvest aid compounds. The field of harvest aid utilization includes a wide variety of primary effects, including the defoliation of the crop plant; the desiccation of its leaves, stems, and other aerial organs; the control of late-season regrowth (e.g., for cotton); the promotion or inhibition of fruit or flower abscission; the concentration of crop maturity; and the enhancement of consumer-preferred quality factors.
Under normal conditions, many crop plants do not mature uniformly or in a timely fashion that would facilitate an efficient and optimum harvest, either due to equipment scheduling or weather considerations. Crops such as cotton, potato, sunflower, and seed legumes require either desiccation or defoliation before harvest can be effectively accomplished. Thus, for example, when cotton is not defoliated the leaves can interfere with mechanized picking apparati which are frequently employed. Also, leaves can contaminate the cotton lint with trash or green stain, which reduces the quality of the fiber or reduces the efficiency of the ginning process. Likewise, potato vines need to be desiccated for efficient mechanical digging. In addition, upon desiccation of potato leaves and stems, the tuber skin matures and becomes less susceptible to damage from the digger and postharvest handling. Seed legumes and sunflowers are also mechanically harvested, and this process is facilitated if the leaves and stems are removed or desiccated. As with cotton and potato, such defoliation or desiccation also ripens the seed uniformly, accelerates the rate of seed maturation, and conditions the pod or head for easy harvest.
Among the compounds which have been shown to exhibit herbicidal activity in the past are certain substituted thiadiazole ureas. For example, U.S. Pat. Nos. 4,066,436, 4,217,459 and 4,141,717, all issued to Kirkpatrick, disclose benzylthio-substituted thiadiazoleureas which are useful as herbicides. Somewhat similarly, U.S. Pat. Nos. 4,175,081 and 4,182,712, both issued to Driscoll, claim alkoxyalkyl and cycloalkyl-substituted thiadiazoleureas respectively, which compounds are shown to be active herbicides. Moreover, U.S. Pat. No. 4,128,412, issued to Metzger et al, shows alkyl- and aryl- mercapto-1,3,4-thiazol-5-yl-ureas useful as herbicides.
While the above described patents show compounds which function as herbicides, it would nonetheless be desirable to possess additional compounds which would function as herbicides, as well as compounds which would function as plant growth regulators, particularly as defoliants--the latter being a use not suggested by either the Kirkpatrick, Metzger et al or the Driscoll patents.
Accordingly, it is an object of this invention to provide novel compounds which will function admirably as herbicides and/or as plant growth regulators.
It is a further object of this invention to provide a process for the production of such novel compounds.
It is yet another object of this invention to provide novel intermediates useful in the production of said novel compounds.
It is still another object of this invention to provide herbicidal and/or plant growth regulatory compositions comprising said novel compounds.
The foregoing and additional objects will become more fully apparent from the following description and Examples.